1. Field of the Invention
This invention relates to a multi-pane glass glazing unit.
Such units are used for residential and commercial construction where controlled light transmittance and low sound and heat transmittance is desirable.
2. Description of the Prior Art
Units of this type and their properties are described in the Canadian Building Digest, put out by the Division of Building Research, National Research Council of Canada, October 1963 in an article "Factory-Sealed Double-Glazed Units" by Solvason and Wilson.
The structure described in this article is a typical insulating glass unit having two panes spaced-apart by a hollow metal spacer containing a desiccant surrounded by one or two sealants between the frame and the pane. One disadvantage of this type of structure is that the air in the space between the panes readily conducts heat and sound. Another disadvantage is that the glass panes pump, i.e. they bow in and out with barometric or temperature changes. This interferes with the aesthetic qualities of the structure since reflections are distorted. It is also destructive to the seal and predisposes the the units to breakage.
Another problem with a metal spacer is that heat is transferred at the edges causing interior perimeter condensation and thermal stresses which also predisposes the unit to breakage. Further, the desiccants are expensive and tend to affect the internal air pressure of the unit. At low temperatures, the desiccant can absorb nitrogen from the air causing the glass to bow in. At high temperatures, the reverse takes place.
In an attempt to overcome these problems, very expensive glazing designs are used with sophisticated sealants with movement capabilities to contain the glass edges.
The types of structure described represent nearly all the production of insulating glass units in the world.
The applicant proposes to depart from this normal commercial pattern in overcoming the problems by the use of a structure in which there is a partial vacuum between the panes. As far as the applicant is aware, this expedient has not been employed commercially, even though there are examples in the patent literature of the use of a vacuum. In one patent, a double-glazed structure is disclosed in which there is a vacuum between the panes which are spaced-apart by special spacers adhered to at least one of the panes and a sealing compound is applied between the margins only of the respective panes and not on their peripheral edges. The structure is evacuated temporarily by providing an opening within the area of one of the panes through which a hollow stem or stud is embedded as a passage for supplying vacuum. The device is equipped with an alarm system which is triggered by loss of vacuum. This alarm system appears to be the primary purpose of this patented structure.
In another patented double-glazed structure, one of the panes is also provided with an opening within its area through which vacuum is drawn. The opening is connected to a vacuum pump which is controlled by an outside thermostat which applies a temporary vacuum for insulating purposes when required. There is also the suggestion in the patent that an evacuated space between the panes could be hermetically sealed, baked out, and gettered to maintain a vacuum for long periods of time, thereby eliminating the requirement for the vacuum pump. In the actual structure shown, a sealing means in the form of an O-ring is applied between the margins of the respective panes. A frame, which has nothing to do with maintaining the vacuum, surrounds the peripheral edges.
These structures are in the nature of specialty items and do not provide the requirements of a day-to-day multiple glazed structure which can be manufactured commercially and employed in the place of the commercial construction described above. It is not apparent from descriptions of these patents how a practical commercial permanently sealed structure can be manufactured.
The applicant now provides a practical commercial permanently sealed partially evacuated multi-glazed unit.